Analog filters present an indispensable tool for selectively passing or blocking electric signals in systems such as communications networks, analog to digital converters (ADCs), audio systems, radar and/or antenna systems, or other electric/electronic systems. In many of these systems, there is a demand for near ideal, or substantially ideal, filters. An ideal filter perfectly passes signals within the respective pass-band and perfectly blocks out-of-band signals. However, ideal filters are non-causal and have infinite delays. Accordingly, one of the goals of analog filter design research has been to design and build near ideal filter circuits. Near ideal filter circuits have frequency responses characterized by steep cutoff edges, almost-rectangular pass-bands, and substantial out-of-band signal suppression.
Whether in wireless communications networks, radar systems, ADCs or other electric systems, near ideal filters can provide a valuable tool to eliminate (or substantially mitigate) undesired signal interference or to accurately block undesired signals associated with specific frequency characteristics. Accordingly, near ideal filters can allow for efficient use of the frequency spectrum in various communications systems.